Dynavax Technologies Corp. (DVAX) tumbled as much as 60 percent in early trading after its hepatitis B vaccine failed to win the backing of U.S. regulatory advisers as the drugmaker seeks to bring its first product to market. Dynavax fell 57 percent to $1.98 at 7:36 a.m. New York time, after dropping to $1.87. While Heplisav works to treat the contagious liver disease, Dynavax didn’t provide adequate safety data to support approval, Food and Drug Administration advisers voted yesterday. The FDA, set to make a decision by Feb. 24, isn’t required to follow the panel’s guidance. Dynavax, based in Berkeley, California, billed the drug as a way to protect healthy adults 18 to 70 years old. Panel members that called Heplisav promising cited the small number of patients Dynavax studied given the vaccine’s potential to cause rare autoimmune diseases. “Since we have vaccines that maybe aren’t as optimal as we want but are effective, that is too flimsy,” Edgar Marcuse, a panel member and associate medical director at Seattle Children’s Hospital, said during the meeting in Silver Spring, Maryland.